DeprecationWarning: pkg_resources is deprecated as an API about colcon-core HOT 4 CLOSED

The deprecation warning leaks to other packages down the stack though which utilize colcon-core.

More specifically by testing the latest setuptools version on Fedora, colcon-ros and colcon-notification fails due to colcon-core's pkg_resources import.

from colcon-core.

I've been toying with solutions here.

One challenge is that we have functions in colcon-core public API which return pkg_resources classes. This was probably not a great design decision. The corresponding classes in importlib.metadata are not similar enough to be drop-in replacements, so I think we'll need to introduce some sort of wrapper class that looks like the pkg_resources classes.

from colcon-core.

Thanks for beginning to think about a way forward here—we're hitting these warnings when testing colcon plugins on Python 3.10 (in Nix). This is how to silence the warnings in pytest, but unfortunately you can't specify the actual package doing the importing, so it's a bit of a blunt instrument:

[tool.pytest.ini_options]
filterwarnings = [
  # This is transitively imported by colcon-core.
  "ignore::DeprecationWarning:pkg_resources",
]

A further complexifier is that the replacement functionality in importlib isn't available in Python 3.8, so either the old implementation must also be retained as long as Ubuntu Focal is a target, or else a dependency must be introduced on a pypi package supplying backports of the new functionality, eg:

• https://pypi.org/project/importlib-metadata/
• https://pypi.org/project/importlib-resources/

from colcon-core.

a dependency must be introduced on a pypi package supplying backports of the new functionality

It seems that python3-importlib-metadata is available for Focal as a deb. It is my intent to declare a dependency on that package conditionally on the interpreter version.

As far as I can tell, it does mean dropping debs for Bionic which reached EOL this past May.

from colcon-core.